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Title: Evaluation of Exotic Parasitoids and Predators in Field Cages. Chapter 8 in: Biological Control of Bemisia: a Review of the Interagency Research and Implementation Program in the United States, 1992-2001)

Interpretive Summary: Sweetpotato whitefly biotype 'B' (= silverleaf whitefly)is a major pest of field, vegetable and ggreenhouse crops in warm climates around the world. It invaded the U.S.A. during the late 1980's and spread rapidly across the southern U.S.A. The impact of the whitefly was especially severe in agricultural production in the southwestern desert valleys in Arizona and California resulting in major economic losses in cotton, alfalfa, melons, and winter vegetables. Naturally occurring biological control agents were ineffective against this invader. Foreign exploration for new agents was undertaken, and field evaluations of introduced natural enemies were conducted in the Imperial Valley, California, to identify effective new species to establish against the whitefly on cantaloupe, which is a key whitefly host requiring control measures in southwestern desert valleys. Evaluations compared 15 species of parasitic wasps from 13 different countries with the native parasite species. One predatory beetle from India was also evaluated. The best-performing species included parasitic wasps from the United Arab Emirates and Ethiopia - both regions with very similar climates to the Imperial Valley. The Ethiopean species has since become established in desert valleys.

Technical Abstract:
Field-cage evaluations of introduced non-indigenous parasitoids in the genera Eretmocerus and Encarsia comprising 8 species of Eretmocerus and 7 species of Encarsia from 13 different countries were conducted during 1997 in the Imperial Valley, California, to identify effective new species or geographic populations for establishment against Bemisia tabaci strain ‘B’ on alfalfa, broccoli, cantaloupe, and cotton, all of which are key host crops of Bemisia tabaci biotype 'B' in southwestern desert valleys in the U.S.A. A predatory coccinellid from India, Serangium parcesetosum, was evaluated separately. The best-performing species and geographic populations parasitoids in these evaluations were then compared again on cantaloupe, a key crop for spring whitefly buildup, and also on citrus, an overwintering host. These evaluations compared geographic populations of E. mundus from Spain, India and Israel, E. hayati from Pakistan, E. emiratus from the United Arab Emirates, and E. near emiratus from Ethiopia with the indigenous species E. eremicus. The number of progeny produced per female in the F generation was the measurement of efficacy. The best-performing species included Eretmocerus emiratus and/or E. near emiratus from the United Arab Emirates and Ethiopia with more than 66 mean progeny per female, and the Israeli and Spanish populations of E. mundus, with 55 and 51 mean progeny, respectively. These species originated in regions with very similar climates to the Imperial Valley. The species which eventually became dominant following field releases was E. emiratus / nr. emiratus from Ethiopia.